Managing boulders on your gold placer mining cut.
A lot of placer mines have a high percentage of boulders in the pay streak.
One of the ways to manage these is to use them to your advantage. I like to stack them up on the side of the next cut. The reason for this is to essentially build a rock retaining wall for the purpose of clearly defining your next cut as you strip down to it.
This also helps keep dilution of the pay gravels from the overburden by using these boulders as a wall. Boulders are much easier to rake out and simply throw them back into your worked pit. I also like to use discarded stumps and trees along the edge if I have to. These can be a bit messy to work with, and the wood can come back to haunt you in your settling pond with the duff and tree bark plugging your intake screens if you are recirculating your water. This is something to keep in mind.
Materials management is the number one priority on any placer mining project.
Project management of placer operations in materials management is so important to the success of an alluvial mining project.
You can see here we are setting up the pit for the last lift of a cut to strip off the remaining 18 ft of overburden. Overburden will swell as much as 50% and can cause havoc if you do not plan accordingly.
All gravel and overburden has a swell factor and you will come to grips with that in short order after you handle your material a few times. Your screen analysis is usually a pretty good baseline and you need to learn to trust those numbers, then adjust accordingly.
Every operator must share any discoveries you find during the shift as far a boulders, tight gravel or any other operating difficulties you may encounter. As a mine manager you need to study each and every detail that your crew is encountering and plan ahead for any anomalies that your mining plan may encounter. Just when you think you have it all under control there is always something that comes out to bite you. Weather, ground water, materials consistency, even manpower fatigue. You must as a mine manager stay multifaceted to every detail and stay on it and do not become complacent.
Overburden management takes experienced operators and management.
I was stripping some deep ground I had some years back. My two D-8's blade to blade pushed 25 to 30 yards a cycle.
I also had a D-9G and we set the D-8s on both sides and were pushing 60 yards plus on the downhill runs per cycle.
The overburden ratio to pay gravel was up to 20 to 1.
Overburden management is the key focus and number one priority to get it right. You have to have experienced operators and management, hands on at all times to keep it in balance. You have to keep pay gravel going to the plant in accordance to your overall mining plan.
~ Rob Towner